1. Field of the Invention
The invention relates to a sealer used for a bolt coated with a sprayed preservative coating, a fastener to be fastened to an object including a sprayed preservative coating composed of aluminum, zinc-aluminum alloy or aluminum-magnesium alloy, based upon a sprayed coating composed of zinc, aluminum or alloys thereof and coated for the purpose of anti-corrosion of steal defined at JIS H 8300: 2005 “Spraying zinc, aluminum or alloys thereof” in Japanese Industrial Standard (JIS), for instance, a bolt, and a method of fabricating a bolt.
2. Description of the Related Art
As countermeasures to corrosion of a structure composed of steal, such as a steal column of a highway bridge, a high corrosion-resistant alloy is sprayed onto surfaces of such a steal structure in a factory to thereby form a high corrosion-resistant coating thereon. Such a steal structure is necessary to be assembled in a construction site for its structural reasons, and hence, is often assembled in a construction site by means of high tensile bolts (HTB) and nuts through the use of spliced plates. However, since high tensile bolts and nuts are not designed to be coated with a high corrosion-resistant coating unlike a steal structure, high tensile bolts and nuts are shorter in durable years than a steal structure, and hence, a maintenance has to be carried out in accordance with durable years of high tensile bolts and nuts.
Thus, high tensile bolts and nuts are desired to be coated with a high corrosion-resistance coating like surfaces of a steal structure. For instance, Japanese Patent Application Publication No. H3 (1991)-41207 suggested a bolt, at least a threaded portion of which is coated with a sprayed layer composed of molybdenum, chromium, tungsten or alloys thereof and having a thickness in the range of 10 to 150 micrometers. Japanese Patent Application Publication No. 2004-176901 suggested a bolt including a threaded portion onto which rigid particles each having a particle diameter of 10 micrometers or smaller are attached by high-speed flame spraying.
In order to use high tensile bolts and nuts in the same durable years as that of a steal structure coated with a high corrosion-resistant coating, it is considered that a high corrosion-resistant coating is necessary to be formed entirely on high tensile bolts and nuts as well as a threaded portion of a high tensile bolt like the bolts suggested in the above-mentioned Publications. However, fastening high tensile bolts and nuts, both of which are entirely coated with a high corrosion-resistant coating by spraying, to a steal structure, it was found that a desired axial force was not gained, even if high tensile bolts and nuts were fastened with a predetermined screw torque.